1. Field
The present disclosure relates to cathode active materials, and cathodes and lithium batteries including the cathode active materials.
2. Description of the Related Art
As a cathode active material for a lithium battery, a transition metal compound or an oxide of these transitional metal compounds and lithium, such as LiNiO2, LiCoO2, LiMn2O4, LiFePO4, LiNixCo1-xO2 (0≦x≦1), or LiNi1-x-yCoxMnyO2 (0≦x≦0.5, 0≦y≦0.5), is used.
LiCoO2 is relatively expensive and has a limited capacity of about 140 milliampere-hours per gram (mAh/g). In addition, when a charging voltage of LiCoO2 is increased to 4.2 volts (V) or more, 50% of the lithium is removed to be present in the form of Li1-xCoO2 (x>0.5) in a battery. Li1-xCoO2 (x>0.5) is structurally unstable and during charging and discharging, a capacity thereof substantially decreases.
A cathode active material, such as LiNixCo1-xO2 (x=1, 2) or LiNi1-x-yCoxMnyO2 (0≦x≦0.5, 0≦y≦0.5), has low structural stability at high voltage.
Accordingly, there is a need to develop a cathode active material having high capacity and having improved structural stability at high voltage to prevent a decrease in discharging voltage, leading to an increase in lifetime characteristics.